The electoral college is far from a perfect way to elect presidents, but that doesn’t mean every “reform” offers an improvement. A case in point: a Michigan Republican’s proposal to apportion the state’s electoral votes by congressional district, replacing the standard method of awarding all electoral votes to the statewide winner. The only rationale for the new method: It would help Republicans.

Here’s how Michigan’s proposed system would work. The statewide winner would get two at-large electoral votes. Then vote tallies in each congressional district would decide the other 14 electoral votes, one apportioned to each district. If you feed the 2012 presidential election results into this proposed system, Mitt Romney winds up beating President Obama 9 to 7 in electoral votes, even though Mr. Romney lost the state by nearly half a million votes. That’s because Michigan’s Democratic voters are packed into a small number of congressional districts.

What if every state moved to Michigan’s proposed congressional district system? (Nebraska and Maine already use versions of it.) The result would still be a pronounced pro-Republican bias, for two reasons. First, Republicans enjoy structural advantages — some natural, some gerrymandered — in the drawing of congressional district lines. Second, awarding two at-large votes to the winner of each state would help Republicans because there are many sparsely populated states that Republicans typically win and a few very populous states that Democrats tend to carry.

Had a congressional district-based electoral college system been applied nationwide in 2012, Mr. Romney would have taken 274 electoral votes to Mr. Obama’s 264, according to the calculations of David Hopkins, a Boston College political scientist. Using data from every presidential election between 1956 and 2004, a 2012 analysis in the journal Statistics, Politics, and Policy found persistent and significant pro-GOP bias under such a system.

Of course, candidates wouldn’t conduct campaigns the same way if the rules were different; they would campaign in tight districts across the country rather than focusing on swing states, for example. But Mr. Hopkins figures that only 30 or 40 House seats are all that competitive, and Democrats would have to take the vast majority of them to win presidential elections — possible in a very good year, but very hard all other times.

It is, as we all know, possible to lose the popular vote and win the electoral college. Under the Michigan system, that unfortunate outcome would be far more likely. There are some potentially helpful electoral college reform ideas that deserve further consideration and analysis. The Michigan proposal, based on raw partisanship, is not one of them.